Studies on Establishment of Cropping Systems in Common Stocks (Matthiola incana R. Br)

V. Varietal Difference of Flowering in Branching Stocks Grown at Various Temperature Schemes

Abstract

In this experiment flowering periods of branching stock plants sown in the summer were examined. In addition, intercultivar differences in temperatures allowable for flower bud initiation and flowering, and difference in response of flowering of pinched and non-pinched seedlings to low temperature conditions were investigated, using extremely early, early, medium, and late flowering stock cultivars.
1. Shoots of seedlings of 12 cultivars sown on August 6 were pinched immediately above the 10th node from the basal point and grown thereafter in an unheated plastic house. Every cultivar initiated flower primordium formation from October to November and flowered from the beginning of December to the middle of March in the order of extremely early, early, medium and late flowering cultivars. Mean temperatures at the time when flower bud initiation was observed were 22°C in the extremely early, 18°C in early, and 13°C in both medium and late flowering cultivars.
2. Seedlings with 2 unfolded leaves were planted in glass-houses where minimum temperatures were maintained at about 3°, 8°, 13°, 18°, and 23°C. Shoots of most seedlings were pinched above the 12th node from the basal point.
At minimum temperatures higher than 23°C, about 75% and 50% of the treated plants flowered in the extremely early flowering cultivar, ‘Iwaiaka No. 1’and‘Sevenweek Trysomic Dwarf Double’, respectively. At minimum temperatures higher than 8°C, from 70 to 100%, and about 17% of the treated plants bloomed in the early flowering cultivar, ‘Iwaiaka No. 2’, ‘Wakazakura’, and‘Dwarf Ten-week’, respectively. All of the medium flowering cultivar, ‘Kanchidori’, flowered at temperatures higher than 13°C. In the case of late flowering cultivar, 75% of the‘Matsudoaka’ plants and 80% of the‘Trysomic Hidouble Lilac-lavender’plants flowered at minimum temperatures higher than 13°C. Thus, it seems that the highest temperature which can induce flower bud initiation are 23°C for the extremely early flowering cultivar, 18°C for the early flowering cultivars, 13°-18°C for the medium flowering cultivars, and 13°C for the late flowering cultivars.
Within temperature regimes allowable for flower bud initiation, flower-budding and flowering periods on both the main and the lateral shoot were earlier in early flowering cultivars than in late flowering ones. The number of nodes to inflorescence was also smaller in the former than in the latter.
When plants before pinching were grown under temperatures allowble for flower bud initiation, the number of nodes to inflorescence on the lateral shoots of all the pinched plants was somewhat decreased below the number of nodes to inflorescence above 12 nodes on the main shoot of non-pinched seedlings.
In all cultivars, there was little difference between two treatments in the number of nodes to inflorescence on the lateral shoots. In one of the treatments seedlings were grown under allowable temperatures from the 2-leaf stage, and in the other treatment the seedlings received low temperatures only after the pinching. Number of days from the pinching to the flower-budding and the flowering was somewhat decreased by low temperature treatments after the pinching.
3. These results suggested that maintaining the temperatures above the low temperature regime allowable for flower bud initiation for a certain period is necessary for the production of cut flowers that have the stalk of sufficient length.